Hydraulic classifier



y v2,857,050 HYDRAIJLICv CLASSIFIER 5 'sheets-sheet 1' Clear Waterv Overflow Discharge Sands VB' rnill C/.kNebel I n l I vATTQRNEY 62 52a Steady Flow- Oct. 21, E. c. NEBEL HYDRAULIC CLASSIFIER Filed Jan. 27o. `1955 5 Sheets-Sheet 2 Feed.

Fig. 2. f

v 70 lj'ines` Dischurge t Pulsoting Flow y Clear Waterv 55 Overflow Hutch 55f Sends Discharge 55]' Y l INVENTOR Emil C. Nebel ATTORNEY I Oct. 21, 1958 v E.C.NEBEL "2585-175050 .x-IYDRAULIC 'CLASSIFIER Filed Jan. 2o. 195,5

Discharge Fig'.l 43. r

mvENrroR kEmil C. Nebel f ATTORNEY OFL Z1, 1958 E. c.-NEBE| I 2,857,050

HYDRAULIC CLASSIFIER Filed Jan. 20. 1955. 5\Sheets-Sheet 4 Discharge 'I l 1, Fig. 4.

by Fig. 5.I ,i

i INVENTR Emil lC. Nebel Oct. 21, 1958 E. c. NEBEL HYDRAULIC CLASSIFIER Filed Jan. 2o. i955 5 Sheets-Sheet 5 Clear Water Overflow Fig. 6.'

Hutch Discharge lNvx-:NToR

il C. Ne el BY h y 1/ ATTORNEY Sands Discharge nited States Patent HYDRAULIC CLASSIFIER Emil C. Nebel, Westport, Conn., assignor to Dorr-Oliver Incorporated, Stamford, Conn., a corporation of Delaware Y Application January 20, 1955, Serial No. 483,049

16 claims. (ci. 209-159) ...This invention relates to the hydraulic classification treatment of pulps containing a range ofparticle sizes from fine to coarse, as exemplified by metallurgical pulps or pulps of wet-ground ore, whereby the particles of the mixture are classified into a coarse and a fine fraction of sizes, herein also termed the coarse fraction and the lines fraction, or else the oversize and the undersize respectively.- The coarse fraction will contain substantially all particlev sizes below, and the fines fraction substantially all sizes above the so-called cut or point of fractionation.

A well known application of such two fraction classifiers lies in the field of continuous closed circuit grinding of metallurgical pulps where the classifier operates in circuit with a wet grinding mill, and in which the mill delivers to the classifier a pulp containing particles ranging from iine to coarse, and the classifier produces a coarse particle fraction to vjoin fresh pulp feed for return to the mill to be further comminuted while the fraction of iin'e particles leaving the classifier is being eliminated from the circuit.

Hydraulic separation of particle sizes as herein contemplated takes place in a pool to which the pulp is fed while the coarse fraction is withdrawn from'the bottom of the pool and the fines fraction overflows from the pool across a weir. The mixture of particle sizes while-in transit through this pool is kept mobilized or in a state of teeter by being subjected to the effect of upward ow of auxiliary so-called hydraulic operating water rising from the bottom of the pool at a controlled velocity or rate. In this way, a desired coarse fraction above a certain mesh ,size will collect at the bottom of the pool to be withdrawn therefrom, while a corresponding fraction of fine sizes with its carrier water overflows from the pool. In such classification apparatus it is important that controls be provided whereby the point of fractionation or lcut between the oversize and the undersize can be readily established and accurately adjusted. For example, if the feed be of a run containing particle sizes ranging, say, from 28 to 200 mesh, then it should be possible, for example, to make a clean split at say l0() mesh, yet it should be possible to readily lshift the cut to, say 48 mesh. This calls for providing simple and effective means for soadjusting or shifting the cut while deriving the respective size fractions clean, that'is -with a minimum of stray ,sizes admixed thereto. For example, the importance of producing a clean coarse fraction is apparent 'where the ,classification apparatus operates in closedfcircuit with a we t grinding mill, the mill to receive coarse fraction particles for 'regrinding, and where the Vadmixture of an appreciable amount of undersize or stray sizes would burden the circulating load through the mill and would accordingly reduce its eciency whole. 4 v

Another :problem is that such apparatus should be capable. of handling effectively a feed 'slurry -or pulp as well as Athat of the circuit as a 857,@50 c patented on. 21, 195s a a containing a relatively wide range ofparticles from rela# tively very fine to relatively very coarse.

Othery problems encountered are to d erive the overflow of the lines at the'highest possible density, or else to operate' with a minimumlof operating water required, even though relatively very coarse particles at the bottom of the pool mustbe Iinduced to migrate towards the underflow discharge. c

In view of these problems, it should be understood that when operating under the desired upow classification and teetervv conditions there are established and maintained in the pool a coarse v solids zone at the bottom, a iines zone at the top, and an intermediate teeter zone of mixed particles of both fractions. The lines fraction is delivered by overliow `from the top zone. The coarse particle fraction is allowed to discharge from the bottom zone at a rate which is automatically controlled in response to density r`variations in the teeter bedl of the pool, in such a manner thatI a lowering of the pulp density below a desired value is at once corrected by a restraining or throttlingv of the coarse fraction discharge, while a rise inpulp density above the desired value is corrected by increasing the rate of coarse fraction discharge.

In other words, the coarse fraction discharge is thus automatically controlled to maintain a substantially constant pulp density inthe teeter bed, thereby in turn maintaining a desired cut defining the point of size frac-v tionation. For example, in-the patent to W. C. Weber No. 2,320,588 such coarse fraction `control is accomplished' automatically by way of allowingthe coarse material from the bottom zone Vto migrate through a passage at the bottom and by Way of a so-called sands seal over a submerged weir into aclear-water chamber representing a clear water column maintained in hydraulic balance with the pulp columnas represented b Y theV effective depth of the p ool.

Another modeof coarse fraction discharge control is by way of controlling spigot discharge directly from the t coarse fraction bottom zone of the pool.

In order to attain the above mentioned objects, this invention provides classification apparatus in which pulp of mixed particle size's is fed to the pooll While hydraulic operating water is introduced at the bottom of the pool in such a manner and at such a rate that the above defined classiiica't'ionzones andteeter conditions are thereby substantially'maintainableu-In addition to abasic upow 'rate of the operating water or superimposed thereon, this invention proposes'to apply to the pulp bed in the pool upflow pulsations of such frequency, intensity and volume, y

that the largest particles at the bottom of the coarsefraction zone will'tliereby be caused or be induced to migrate along the'botto'mjto the point of discharge.

Inv other Words, the pulse effect of this machine is produced by a separatehydraulic system acting on the upflowing stream of teeter water passing througha false bottom in the form of a screen or constriction plate.

According to one'embodimengthe pool is Vdefined by a tank structure which has a false bottom in the form of a y constriction'plate having aboveit the classication pool proper and below ita water supply chamber. Hydraulic water is fed at acontr'olled rate to the supply chamber from which-the`-water upflows through the constriction plate at a' rate-to sustain the desired teeter condition in the pool. Pulsations are imposed upon the body of operating water in the supply chamber, as by' means of a pulsating 'valve through' which secondary operating water irsvadm'itted to the Ichamber interruptedly in the form of pulsations o f suitable characteristics, .o'r else the `pulsations are imparted by the rapid pumping or liquid displacing reffect "o'f Aa `mechanically actuated diaphragm. Accordingv to one form,l discharging of coarse fraction particles is into a receiving 'Chamber Icprlliing slew f. 3 Y water column in hydraulic balance with the pulp column as represented by the effective depth of pulp in the pool. According to another form, the tank structure has the pool above and the watersupply chamber below the constriction plate while the coarse fraction material is spigoted directly from the bottom zone ofthe pool. A density-responsive control device adjusts the spigot discharge valve automatically in a manner whereby pulp v density in the pool is maintained substantially constant at pool directly through a spigot discharge valve which is automatically settable by means `of a control device responsive to pulp density changes inthe pool.

Still another embodiment presents a tank structure in which a false bottom in the form of a constriction plate is vertically vibratable between the body of' pulp above and the body of operating water below. A main supply of operating water-,enters a chamber below the constriction plate to rise therethrough ata steady rate for maintaining the classification zones or teeter condition ,in the pool as above dei-ined, while the vertical vibrations of the constriction plate serve to provide the additional inducement hydraulically for the coarsest particles in the bottom zone to migrate towards discharge. Coarse fraction material discharges through a submerged passage,

4through a sands seal and lover a submerged weir into `a receiving chamber representing a clear water column in hydraulic balance with the pulp column as represented `by the elective depth of the pool orthe effective specilic gravity thereof. y

According to one feature, two pulse eiects are applied in combination ink such a manner that the impact curve of the compound effect of these eiects upon the teeter bed may be rendered more nearly inthe form of a sine curve instead of asia square curve. In'this way there is attainable a pulsation impact 'y curve better suited for the kindY ot classication operation` contemplated by this invention; i y Y In summary, this invention provides a classilcationrmachine in which pulse effect is added `to thelow ofteeter water upflowing through the pool of pulp undergoing classilication treatment, whilethe rate of discharge of coarse fraction material from the bottom zone of the Ipool is automatically controlled in response to pulp density changes in the pool, in a manner whereby the pulp density is kept substantially constant, and thereby the cut or point of particle size fraction is maintained at a desired value. l

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and ally changes that fall withinthe metes and bounds of the claims, or of forms that are their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

In' the drawings:

v Figure l shows the invention'embodied in a tank structure of the constriction plate typewith coarse fraction discharge over a weir into a receiving chamber, with pulsations supplied by a pulsating watersupplyvalve, and coarse fraction discharge control `by means of controlled hydraulic balance of the clear waterv column in the receiving chamber as against the pulpy column in the pool.

Figure 2 shows the machine substantially resembling that of Figure l, except for the fact that the pulsations are membrane-induced.

Figure 3 shows an embodiment of the machine differing from the Figure 1 and 2 embodiment by the provision of direct spigot discharge of the coarse fraction material, and of corresponding pulp density responsive discharge control devices.

Figure 4 shows one embodiment of the machine difiering from the Figure l and 2 embodiment by the provision of overhead supply of operating water to the solid tank bottom, while employing the Figure 3 provision of direct spigot discharge of coarse fraction material from thev bottom zone of the pool with pulp density responsive automatic control devices for the spigot discharge.

Figure 5 is a cross-sectional view taken on line 5-5 of Figure 4.

Figure 6 shows an embodiment ofthe machine, which dilers from the preceding embodiments by employing a constriction plate which is vertically reciprocable or vibratable between the pool of pulp and the water supply chamber.

The machine of the Figure 1 embodiment is represented by a tank structure for instance, round or square in cross section, comprising an outer wall structure 10 having a conical or hopper-shaped bottom portion 11; an inner wall structure 12 which is upwardly and downwardly open-ended and has lixed relationship with respect to the surrounding outer wall structure 10; and a supply chamber 13 for operating water disposed substantially within or surrounded by the hopper-shaped bottom portion 11, and comprising a horizontal top plate in the form of a constriction plate 14, a vertical wall portion 1S, and

wa hopper-shaped bottom portion 16. The inner wall structure 12 is iixedly connected with and supported by the outer wall structure 1t? by means of a cover plate 17 dening above it an overow launder 18 yfor receiving and discharging the overflowing lines fraction,.and below it a receiving chamber 19 into which the coarse fraction particles will discharge. That is to say, the inner wall structure 12 together with constriction plate .14 defines a pool of pulp P undergoing classication treatment while the outer tank wall structure 10 with hopper-shaped bottom 11 and cover plate 17 denes the receiving' chamber 19 surrounding the pool P" as well as the water supply chamber 13.

The vertical wall portion 15 of water supply chamber 13 rises a distance h1 sufficientlyy above` the constriction plate 14 to constitute a submerged discharge weir 20 to lsurround the lower tree end of the inner wall structure 12 in horizontally spaced relationship therewith. The Ylower end of inner wall structure 12 in turn is spaced a distance h2 upwardly from the constriction plate 14 to constitute therewith al coarse fraction discharge passage 21, there being provided a slight vertical overlap O between the submerged weir 20 and the lower end of the inner wall structure 12, constituting what is herein termed a sands seal effective between the pool P and the body of water in the receiving chamber 19. The structure which constitutes the water supply chamber 13 is supported upon the outer wall structure as by brackets 13a which may be adjustable if desired so that the height of passage 21 may thereby be rendered adjustable.

A supply pipe 22 penetrating the outer as well as the inner wall structures, leads into the water supply charnber 13 for supplying operating water thereto. The pipe 22 in turn receives a steady or uniform flow of pressure water from a lirst branch pipe 23 provided with control 'valve 24. A second branch pipe 25 provides a pulsating ow of operating water to enter the supply pipe 22 by way of a pulsator device 26 which of itself is well known.

The introduction of feed pulp into the pool P is indi# cated by a feed pulp inlet pipe 27, while a discharge conduit 28 indicates the passage of the overowing fines fraction from the launder 18 and a bottom outlet 29 provided wit-h control valve 30 indicates the ,discharge :of coarse fraction 4'material vfrom th'e l-liopper shaped 'bottom .11 `of the receiving chamber 19. rihe outerftank structurelf'() has an upward stack-like extension 31 laterallyy disposed to accommodate a clear water column 32 the top level L1 of which is defined by an overflow pipe 33 comprising a stack of removable rings 34 for adjusting the super-elevation S of clear water level L1 and the top level L2 of the pool of pulp. Y

.A so-called hutch discharge connection is provided in the form of a pipe 35v leading fromV the bottom of the water supply chamber 13 extending through an opening in the vhopper-shaped bottom I11. That is to say, any line particles of pulprthat may lind their way from the pulp bled or pool of pulp downwardly through the constriction plate 14 may be discharged from the water supply chamber 13 through pipe 35 by way of a valve 36 .provided in the pipe. The pipe 35 while connected rigidly with the supply chamber 13 is sealed yoff against the wall of bottom 11 by means ofa conically shaped rubber sleeve 37 having a narrower outer end 38 surrounding and hugging pipe 35 and sealingly fastened thereto, and having a flanged end 39 sealingly fastened to the inclined wall of bottom 11. The pulsator device 26 of'known construction comprises an annular chamber-40 concentric with and fastened to branch supply `pipe 25, formed by a shallow casing 41 vhaving mounted thereon conically shaped valve seat member 42 upon which closes a spring-loaded valve member 43 movably connected to the outer flanged end -portion 41a of casing 41 by means -of a diaphragm member M. Spring pressure is `exerted upon the valve member 43 by a compression coil spring 44 conned between the valve .member 43 and a yoke structure 45 rigidly fastened upon the flanged end portion 41a of casing 41. r'Ihe spring loading upon the vvalve member is adjustable -as indicated by Ia screw spindle 46 with lock nut 47. The annular chamber 40 has a vsupply pipe 48 for supplying pressure water thereto.

The pulsator device 26 functions to convert the steady Water pressure supplied by pipe-48 into pressure pulsations reaching the body of water in 'the supply chamber 13 and superimposes the water pressure of the steady or uniform water supply entering -the chamber 13 'from ibranch pipe 23.

That is to say, the continuous water pressure from supply rpipe 48 acting upon thediaphragm M lifts ythe valve member olf its seat 42 sufliciently to allow the supply pressure to drop -momentarily as the water surges past the valve into pipe 22 and into chamber 13. This mo- -mentary pressure drop again allows the valve tofclose, so that the normal water pressure from `pipe 48will restore itself to the point of again `lifting the valve member 43. The frequency and character of 'these pressure pulsations can be adjusted by way of adjusting the ypressure of spring 44.

The operationof the Figure 1 embodiment of themachine is as follows:

While pulp of a suitable concentration :containing a range of particle sizes from lines vto coarse, is beingsupplied continuously to the pool P from vfeed pipe 27, operating water continuously enters the 'chamber 13 below the constriction plate 14 at a rate great enough Ito maintain the material in the pool P in -a teeter condition suitable for effecting the desired classification.

That is to say, hydraulic upflow or `hindered settling conditions are thus maintained whereby there 'are established in the pool substantially three classification vzones, namely a bottom zone a of course particles for underow discharge from the pool, a top zone b of lines 'to overow from the pool, and an intermediate or teeter zone c of mixed particle sizes in teeter condition.

The pulsations which are superimposed upon the uni- `form rate of water supply into the supply chamber 13 have the effect of maintaining the layer of .coarse fraction particles closest to the constriction lplate in a state of fluidity enabling them to migrate towards and through the discharge Ipassage 21, so that these coarse fraction particles will then pass through the sands seal represented by the overlap o and spill across the submerged weir 20 into the receiving cham-ber 19. v

With the pulp in the pool thus maintained in a fluid lor teeter condition, control of the fractionation point or cut .is here affected by way of balancing the height of the pulp column H1 in the pool defined by overflow level L2, against the height -of a clear water column H2 dened by overflow level L1. That is to say, by adjusting the clear water overllovv level L1 upwardly the fractionation lpoint can be shifted towards the coarse particle end of the size range, lwhereas adjusting the overflow level L1 downwardly will move the fraction point towards the line particle end of the range.

However, by maintaining the clear water overflow at a chosen level L1 the average density ofthe pulpv in the teeter bed of the pool is maintainable at a constantpvalue, which :in turn maintains the fractionation or cut vsubstantially constant at a desired point. Fine vrparticles which may nd their way downwardly through the constriction plate 14, will collect at the bottom of supply chamber 13 whence they can be withdrawn periodically Vby way of manipulating the valve 36 of the hutch discharge pipe 35.

The Figure 2 embodiment is similar to the VFigure l embodiment :in its general structural organization, but differs with respect to the addition of pulsation inducing means in the form of liquid displacing means such as diaphragm means associated with the water supply chamber 13 and reciprocatory actuating means therefor.

Hence, the tank structure of the Figure 2 embodiment comprises an outer wall structure 49 having a conical vor 'hopper-shaped bottom portion 50; an inner wall structure 51 which is upwardly and downwardly open-ended and has fixed relationship with respect to the surrounding outer wall structure 49, and a supply chamber 52 lfor hydraulic operating water and disposed substantially within or surrounded by the bottom portion 50, and which supply chamber comprises a horizontal top plate in the form of a constriction plate 53, a vertical wall portion 54, and a conical hopper shaped bottom portion55.

The conical portion comprises a top section 55a and bottom section 55h' both ixedly mounted with respect to the Ysurrounding tank structure, and an intermediate sec'- tion 55C connected to the ltop section 55a'and the bottom section 55h by means of correspondingly shaped conical membranes 55d and 55e respectively.

.Up and down reciprocation or vibration is imparted to the intermediate conical bottom section 55c by means of actuating mechanism here shown tov comprise a pair of vertical actuating rods 55f and 55g extending from 'the section 55c downwardly through the hopper-shaped bottom 50 in liquid-sealing relationship therewith. The lower ends of the actuating rods 55f and 55g are interconnected by means of a yoke member 55h to which the up and down movement is imparted by an eccentric device 55i driven by a motor 55k. Sealing relationship between the actuating rods 55f and 55g and the tank bottom 50 is established by means of rubber jackets 55l and 55m having their upper vends sealingly connected to the tank bottom and their lower ends sealingly connected to the respective actuating rods.

The inner wall structure is ixedly connected with Vand supported by the outer Wall structure 49 by means of a coverplate 56 defining above it an overflow launder 57 for'dischargin'g the lines fraction, and below itia receiving chamber 58 into which the coarse vfraction particles will discharge.

` That -is to say, the inner wall structure 51 together with constrictionplate 53 defines a pool o'f pulp P1 undergoing classication treatment, while :the -outer tank wall structure 4,9v with hopper-shaped bottom portion '50 tand 7 Y cover plate 56 defines the receiving chamber 58 surrounding the pool P1 as well as the water supplychamber S2. The vertical wall portion S4 of supply chamber 52 rises a distance h3 above the constriction plate 53 to constitute a submerged discharge Weir 59 to surround the lower free Vend of the inner wall structure'Sl in horizontally spaced tween pool P1 and the body of water in the receiving chamber 52. The structure which constitutes the water supply chamber 52 is supported upon the outer wall structure as by bracket 52.a which may be adjustable if desired so that the height of discharge passage 60 may thereby be rendered adjustable. I

A supply pipe 61 penetrating the outer as well as the inner wall structure, leads into the water supply chamber 52 for supplying operating water thereto. The pipe 61 in turn receives a steady or uniform tlow of pressure water from a first branch pipe 62 provided with control valve 63. A second branch pipe 64 provides a pulsating flow of operating water to enter the supply pipe 61 by way of a pulsator device (not shown) which may be similarv to that shown and described in connection with the Figure l embodiment.

The introduction of feed pulp into the pool P1 is indicated by a feed pulp inlet pipe 65, while a discharge conduit 66 indicates the passage of the overflowing iines fraction from the launder 57 and a bottom outlet 67 with control valve 68 indicates the discharge of coarse fraction material from the hopper-shaped bottom portion 50 of the receiving chamber 58.

The outer tank structure 49 has an upward stack-like extension 69 laterally disposed to accommodate a clear water column 70 the top level T of which is dened by an overflow pipe 71 comprising a stack of removable rings 72 for adjusting the super-elevation Q of clear Water level T over the top level R of the pool of pulp SPI",

The so-called hutch discharge connection is provided in the form of a pipe 73 leading from the bottom of the water supply chamber 52 extending through an opening in bottom portion 50 of the outer tank structure, the pipe 73 being xedly connected to the sloping wall of the tank bottom as by means of a flange 74 welded to pipe 73. That is to say, any ne particles that may iind their `way from the pulp bed or pool of pulp downwardly through the constriction plate 53, may be discharged from the water supply chamber 52 by way of manipulating a valve 733 provided in the pipe. The compound elect of the two pulsation inducing devices in this embodiment makes it possible to modify pulsation characteristics in the shape of the pulsating curve.

The operation of the machine according to the Figure 2 embodiment of the machine is substantially similar to that described above in connection with the Figure 1 embodiment. That is to say, the rate of supply of operatf ing water is controlled in such a manner that in the classilier pool there are established a bottom zone a' comprising coarse fraction solids for underflow discharge from the pool, a top zone b comprising the fines to overow from the pool, and an intermediate zone c' comprising a mixture of the particle sizes in teeter condition.

. The pulp density and fractionation control of the classifier pool of Figure 2 is by means of the clear water balancing column 70 similar to the Figure 1 embodiment. But the characteristics of the pulsations can be inuenced or the pulsation curve be shaped additionally because of the pulsations which are due to the up and down reciprocations of the bottom section 55 in addition to the pulsating'ow of operating water from branch pipe 64.

'Ihe Figure 3 embodiment dilers from the preceding embodiment mainly in that it provides discharge for the coarse` fraction particles through a controlled discharge area or valve, directly from the sands zone at the bottom of the pool. Control devices are provided for automatically adjusting the discharge valve or discharge area in response to density changes in the teeter bed or pool, so that the pulp density and thereby the point of fractionation or cut is kept substantially constant.

The machine of the Figure 3 embodiment is represented by a tank structure 74 which comprises a top portion '75 of the height S1 containing the pulp bath proper and a hopper-shaped bottom portion 76 of the height S2 defined against the top portion 75 by a false bottom constriction plate 7 7. The upper tank portion 75 has a feed inlet chute 78 at one end, and an overflow weir V79 for the ines at the opposite end for the lines fraction to pass into an overow launder 80 having a discharge connection 81. The hopper-shaped bottom portion 76 represents a water supply chamber 82 having a pressure water supply connection 83 into which feed a pair of branch connections 84 and 85, the branch connection 84 to supply a steady ow of operating water, the branch connection 85 to supply a pulsating ow of operating water, as by means of a pulsating device or pulsator similar to the one in the Figure 1 embodiment but here not shown. Control and shut-ott valves for the branch pipes 84 and 85 are indicated at 84@L and 85a respectively. Additional pulsating means are provided in the form of a diaphragm pumping or pulsating device 86 comprising a plunger member or plate member 87 constituting a portion of the hopper shaped bottom 76 and movably connected thereto by means of an annular diaphragm member 88. Drive means 89 are shown for reciprocating or vibrating the plunger plate 87. Fine particles which may enter the supply chamber 82 downwardly through the constriction plate 77 will collect at the bottom of supply chamber 82 whence they can be withdrawn periodically by the manipulation of a hutch discharge valve 82a.

The upper tank portion 75 is of the length l1 comprising the length l2 of the constriction plate proper plus an overhanging length I3 extending beyond the hopper-shaped bottom portion 76 of the tank structure. The overhanging tank portion has a flat solid bottom 89 extending from the outer end of the constriction plate 77, and provided with a spigot discharge connection 90 for the discharge of coarse fraction particles from the pool through a hand-operated shut-o valve 91. Automatic control is accomplished by means of an air pressure controlled rubber spigot valve V, having an inatable rubber annulus N representing the variable throughiiow area of spigot valve V. Density responsive control devices in the form of a relay system E are provided for automatically adjusting the throughow area of spigot valve V in a manner to maintain substantially constant the density of the teeter bed and thus the point of size separation or fractionation between the underiiow and the overow particles.

The automatic control system E for the spigot valve V comprises a clear water balancing column 92 provided with make-up water supply 92, which column communicates with the teeter bed of the pool, and a relay system R operatively interconnecting the balancing column 92 with the spigot valve V so that variations in the height of the balancing column, reflecting variations in density of the teeter bed, will correctively adjust the opening or throughflow area of spigot valve V.

This control system, therefore, may be regarded as comprising a pressure control which senses and responds to changes in the height of the superelevation of the balancing column in pipe 92 over the height of the pulp column in the pool. This pressure control varies air pressure actuating a booster relay system which in turn regulates the air pressure controlling the diameter or throughiiow area of the rubber spigot valve V.

The underflow discharge icontrclsystem thus comprises the stationary open-ended verticalpipe 92 the lower "end of which extends a 'suitable distance into the teeter feed of the pool of pulp undergoing classification lin the tank. If the superelevation of the clear water in pipe 92 should rise, the relay system will actto increase the throughow area of the spigot valve so Aas 'to allow an increased volumn of pulp to discharge until the superelevation in pipe 92 is restored to its normal predetermined level, at which time the spigot valve V will again constrict toa diameter to hold the superelevation level correspondingly. Conversely, if the superelevation in pipe 92 should decrease, the spigot valve V will constrict suliiciently to reduce the throughflow volume of underflow pulp leaving 'the machine, thus in turnreturning the height 0f superelevation in pipe 92 to the normal level.

This relay control system R comprises a master control 93 having pressure communication 93a with the superelevation pipe 92, which master control device respon-ds to changes in the height of the water column of superelevation in pipe 92, and -is adapted to control the application of relay air pressure to the spigot valve V.

vThe master control unit 93 is here shown to be in the form of a Minneapolis Honeywell Pressure Control Type P097A. In that device a bellows 94 communicates with the superelevation pipe 92 which in turn communicates with the teeter bed of the classifier pool. Any change in the height of the water column in the pipe 92 manifests itself by an expansion or contraction of the bellows 94 of pressure control unit 93, which expansion or Vcontraction of the bellows actuates a lever 95 to swing about the fixed knife edges 96 and 97. The motion of lever 95 is transmitted through linkage 9S to a flapper valve 99 the lowering or raising of which regulates the amount of air allowed to escape from an air nozzle 100.

A supply of high pressure air entering the vrelay control system is indicated at 101 passing through a constant pressure regulating valve C. This pressure is reduced by a constriction or adjustable orifice such as provided by an adjustable needle valve unit 102 through which the air passes into a branch pipe connection 103 leading to the air nozzle 100 of pressure control unit 93, as well as into a branch connection 103ad leading to the inflatable rubber annulus N of spigot discharge valve V.

The pressure reduction through the needle'valve 102 is such as to provide the appropriate operating pressure for the pressure control unit 93 and for 'the spigot valve V relative to the static pressure of the pulp column in the classifying pool. A pressure gauge 101a indicates the air pressure entering at the high pressure side of the needle Valve 102. A pressure gauge 101b indicates the pressure at the low pressure side of the needle valve 101.

In the operation of this control system when the superelevation in pipe 92 rises due to an increase in pulp density of the teeter bed, such increase will expand the bellows 94 accordingly, thereby through lever 95 and link 98 raising the flapper valve 99 otithe air nozzle 100 sutiiciently to reduce the air pressure in the rubber spigot valve V, thus increasing the throughflow area thereof until equilibrium or the status quo is restored in terms of pulp density in the pool and height of superelevation in pipe 92. Conversely, when the superelevation inpipe`92 should drop due to a decrease in pulp density in the pool, such decrease will contract the bellows 94 accordingly, thereby through lever 95 and link 98 lowering the liapper valve 99 towards the air'nozzle 100 sufficiently decreasing the throughiiow area thereof until equilibruim or the status quo is restored in terms 'of pulp density in the pool 'and height of superelevation in pipe 92.

In the operationl of the machine according to the Figure 3 embodiment, the application v'of operating water to the supply chamber 82 is substantially similar to that described for the Figure 2 embodiment, 1in that it includes the combination of a pulsating liow of operating water from branch pipe 85 with membrane-induced pulsations which are due to the reciprocations or vibration tof the plate membe'r`87, -these combined pulsations being added to the uniform supply of operating water entering the supply chamber 82 from'branch pipe 84. However, the classification conditions to be maintained in theclassiier pool proper are similar to ythose to be maintained in the embodiments of Figures 1 and 2, in that the supply of operating water including uniform supply plus pulsating flow as well as eXtra membrane induced pulsations is so controlled as to maintain in the classifier pool substantially a bottom zone m of coarse fraction particles for underflow discharge from the pool, a top zone "n of lines to overow from the pool and an intermediate zone o containing a mixture of particle size in teeter condition.

In accordance with this formation of zones 111, "n, 0, the average density in the teeter bed of the classilier pool and hence the point of fractionation are maintained substantially constant automatically bythe operation of the control system E described above regulating the rate of underflow discharge through spigot discharge valve V in response to density changes in the teeter bed of the classifier pool.

The Figure 4 embodiment differs from any of thepreceding embodiments by employing overhead conduit means for the introduction of operating water into the classifier pool.

This machine comprises atank 104 having a solid bottom 105 and side walls 106. The fines fraction overflows by way of a weir 107 as v'represented by the top edge of the tank. The upper portion of the tank is surrounded by an overow launder v103 receiving the fines overflow from weir 107 and having a discharge connection 109. Operating water is supplied Ato the bottom strata of the classifier pool by means of a supply conduit system D which comprises a horizontally extending supply header 110 which in turn has a supply pipe 111 feeding it. Vertical branch pipes 112 extend downwardly from the heady er, each branch pipe 112 having a nozzle head 113 to emit jets of operating water downwardly at a suitable angle "g towards the tank bottom, the nozzle hea-ds 113 accordingly being spaced relatively close to the tank bottom, namely a suitabledistance "d therefrom.

Operating water is supplied tothe vnozzle heads 113 from a source of uniform pressure through a branch pipe 115 provided with control valve v115a and from a source of pulsating pressure through a branch pipe 116 provided with a pulsating vdevice or pulsator 117 similar to the one described in connection with the'Figur'e 1 embodiment, and also having a :control valve 116g.

The introduction of pulp into the tank is indicated by a feed pipe 118, while the underow discharge of coarse fraction from the tank is by a spigot discharge connection 119 leading directly from the bottom of the tank and provided with a manually'operable valve 120.

The rate of underflow ydischarge itself and thus the point of fractionation is controlled by a spigot discharge valve 121 (similar Ato that of the Figure 3 embodiment) having an inflatable annulus 122 whereby the throughflow areaof the valve can be varied in response to density variations in the classifier pool. Automatic control of the spigot valve 121 is effected by means of a control system E' similar vto that described in the Figure 3 embodiment. That is, the changes in the clear water superelevation in a density sensing pipe 123 is relayed to spigot valve 122 through the medium of auxiliary air pressure controlled by a master control Aunit or relay pressure control unit 124 (similar to the unit 93 in Figure 3) to govern the pressure in the inflatable annulus 122 at the low pressure side of an orifice or needle valve unit 124 (similar to unit 102 of Figure l) supplied by a pipe 125 carrying high pressure air thereto. A constant pressure control valve 126 is provided in pipe 125 as well as an air pressure gauge 127. A make-up water clear water supply is indicated at 1.23'f1'for the clear ,water balancing column in pipe 123. Another air pressure gauge 128 indi- 1 1 cates the pressure in annulus 122 of the rubber spigot valve 121.

In the operation ofthe machine according to the Figure 4 embodiment, the application of the operating water to the classifier pool is again controlled in such a manner as to maintain in the pool substantially a bottom zone "p" comprising coarse fraction particles for underow discharge from the pool, a top zone g of fines to overow from the pool, and an intermediate zone r containing a mixture of particle sizes in teeter condition. The operating water applied comprises the uniform ow from branch pipe 115 combined with the pulsating flow from branch pipe 116 and pulsator 117. The operating water issuing from the nozzle heads 113 in the form of jets is directed at a suitable angle towards the tank bottom.

lAs a result there rises from the bottom what is in effect an upward how of Water uniformly distribued over the tank bottom, with the pulsation adequate to maintain the coarse fraction particles at the bottom in a state of liuidity so they will migrate towards the point of underliow discharge, namely towards and into underow discharge pipe 119.

The point of size fractionation is controlled and maintained by automatically controlling the rate. of underow discharging through rubber spigot valve 122, such automatic control being affected by the control system E' in the manner described in detail above for the Figure 3 embodiment of the machine. That control system responds to density changes in the teeter bed of the classifier pool, and applies correspondingly varying relay air pressure to the inilatable rubber annulus 122 of spigot valve 121, in that changes in the clear water superelevation in pipe 123 causes the control unit 124 to correspondingly vary the relay air pressure admitted to the rubber spigot valve V through needle valve 124e.

The Figure 6 embodiment of the machine resembles that of Figure 1 with respect to the provision of the constriction plate, the manner of coarse fraction discharge through a receiving chamber, and the manner of size fractionation control by means of clear Water superelevation control. But a diiference lies in the manner of supplying pulsating effects to the coarse fraction bottom zone of the pool, namely by means of bodily reciprocating or vibrating the lconstriction plate in a vertical direction.

This machine then is represented by a tank structure for instance round or square in cross section, comprising an outer wall structure 128 having a conical 0r hoppershaped bottom portion 129, an inner wall structure 130 which is upwardly and downwardly open-ended and has fixed relationship with respect to the surrounding outer wall structure 128; and a water supply chamber 131 disposed substantially within and surrounded by the hoppershaped bottom portion 129, and comprising a horizontal top plate in theform of a constriction plate 132, a vertical wall portion 133, and a hopper shaped bottom portion 134. The inner wall structure 130 is lixedly connected with and supported by the outer wall structure 128 by means of a -cover plate 135 defining above it an overilow launder 136 for receiving and discharging the overflowing fines fraction, and below it a receiving chamber 137 into which the coarse fraction particles will discharge. That is to say, the inner wall structure 130 together with constriction plate 132 defines a pool of pulp undergoing classication treatment while the outer tank wall structure 128 with hopper-shaped bottom 129 and cover plate 135 defines the surrounding receiving chamber 137.

In contrast with the preceding embodiments, the constriction plate 132 is not fixed to the surounding vertical wall portion 133 of supply chamber 131, but has sealing relationship therewith while being vertically reciprocata- `ble or vibratable with respect thereto in plunger-like lfashion. Actuating means for so reciprocating the constriction plate are here shown to comprise a vertical plunger rod 138 having its lower end rigidly connected to the top side of the constriction plate 132. Theplunger rod 138 is vertically movable in an overhead girder struc- 'ture 139 rigidly supported by the top end of the outer wall structure 128.

The plunger rod 138 is vibrated up and down by a bellcrank lever 140 having a horizontal arm 140a and a vertical arm 140k* which bellcrank lever in turn is oscillated by a vibrating device 141. That is to say, the vibrating device being suspended as by a hanger element 142 is driven by a motor 143, to impart horizontal vibration to the end of the vertical arm 140b of the bellcrank lever, so that the horizontal arm 140a of the bellcrank lever together with the plunger rod 133 and the constriction plate 132 will be vibrated in a vertical direction.

The constriction plate 132 has a marginal upstanding rim portion 144 representing a submerged weir edge 145 across which coarse fraction material from the bottom zone of the pool may spill outwardly into the receiving chamber 137. That is to say, the weir edge 145 rises to have an overlap 146 with the lower edge portion 130a of the inner wall structure 130 even though spaced a distance 147 outwardly therefrom. The lower edge 130a is spaced upwardly from the constriction plate 132 a distance providing a coarse fraction discharge passage Z.

The receiving chamber 137 has a lateral upward extension 14S to provide a clear water balancing column defined by the top end of an overflow pipe 149aL defining the top level K of the clear water column 149. The overow level K is adjustable as indicated by removable rings 150 of the overow pipe, the superelevation of level K over the pulp overflow level in the classifier pool being designated as M1.

The introduction of feed pulp into the pool is indicated by a feed pipe 151. Discharge of coarse fraction particles from the hopper-shaped bottom 129A is indcated by a discharge pipe 129a provided with control or shut-olfvalve 129". Means for introducing operating water into the supply chamber 131 comprise a supply pipe 152 penetrating the outer wall structure 128 as well as the vertical wall portion 133 of supply chamber 131. The supply pipe 152 has one branch pipe 153 providing a steady dow of operating water, and another branch pipe 154 providing a pulsating flow of operating water as by means of a pulsating device (not shown) which may be similar to the one shown and described in conjunction with the Figure 1 embodiment of the machine. These branch supply pipes 153 and 154 are shown to have hand-operated valves 155 and 156 respectively for shut-off or control.

The structures 133 and 134 constituting the water supply chamber is iixedly supported upon the outer wall structure 128 as is indicated by brackets 157. A socalled hutch discharge pipe 158 provided with shut-oft' valve 159 leads from the lowest point of supply chamber 131 through the hopper-shaped bottom 129 of the outer tank structure in sealing relationship therewith, the valve 159 being operable manually for periodically withdrawing any fine particles that may have escaped downwardly through the constriction plate into the supply chamber 131.

In the operation of the machine according to the Figure 6 embodiment, the rate of upow water from the supply chamber 131 is such as to maintain in the classifier pool classification zones substantially similar to those described in conjunction with the preceding embodiments of the machine. That is to say, there is maintained in the pool a bottom zone s of coarse fraction particles for underflow discharge, a top zone u of fines to overflow into launder 136, and an intermediate zone t containing a mixture of particle sizes in teeter condition.

The coarse particles in the bottom zone are maintained in a state of fluidity by the up and down vibration of the constriction plate 132 suicient to cause these coarse fraction particles to migrate outwardly towards and through the discharge passage VZ and over the submerged weir 145 into the receiving chamber 137. The desired point of size fractionation is attained and maintainable by adjusting the' clear water overflow level K relative to the pulp level of 'pool P2 in order to maintain a desired superelevation M1' between these levels.

I claim: v

1. Apparatus for the 'hydraulic classification treatment of pulp containing a mixture of particle sizes ranging from fine to coarse to effect thessepar'ation of the mixture into a fraction of fines and a fraction of coarse particle sizes, defined as undersize and oversize particles, respectively, which apparatus comprises a tank structure to hold a classifying pool defined b'y ahorizont'al bottom and walls presenting over'ow means for discharging the fines fraction from the top of the pool, controllable water supply means providing a flow of operating water for said pool for emitting such operating water at a substantially uniform rate distributively ina manner whereby the water in effect rises in substantially uniform distribution from the bottom of the pool, and whereby in turn there are formed and maintained in said pool horizontal classification zones comprising substantially a lower zone of oversize particles adapted to be discharged through an outlet at Vthe bottom, 'a fines zone o'f undersize particles adapted yto discharge from the top, and an intermediate zone containing a mixture of oversize and undersize particles in teeter condition, controllable discharge means for the oversize particles, and actuating means responsive to lthe density of said pool for automatically controlling said discharge means in response to density changes in said pool to automatically maintain a desired fractionation between 'the oversize and undersize discharging from said pool; characterized by the addition of a flow control device providing rhythmic interrupted ow of water to superimpose upon said flow of operating water for inducing oversize solids in the lower zone to migrate over the tank 4bottom Tto said discharge. A

2. Apparatus accordingv to claim -1 with the addition vof' mechanical pulsating means for further superimposing straight pulsations upon said rhythmically interrupted auxiliary water said pulsating means having an effective reciprocatory member for automatically increasing and decreasing a confined body of water communicating with said ow of operating water.

3. Apparatus according to claim l, in which said horizontal bottom is in the nature of a false bottom constriction plate, and the water supply means comprise a supply chamber defined by said constriction plate and by a solid bottom structure underneath said constriction plate.

4. Apparatus according to claim l, in which said tank structure comprises an outer wall structure having a solid bottom, an inner wall structure surrounded by said outer wall structure and presenting free horizontal bottom edges, a horizontal false bottom member in the nature of a constriction plate spaced downwardly from said free horizontal bottom edges to provide outward passage for the coarse fraction particles, an upstanding discharge Weir provided edgewise upon and along said bottom member and spaced outwardly from said passage in order that coarse fraction particles in said pool migrating to said passage may spill across said weir into a receiving chamber defined below, said inner wall structure together with said bottom member defining the space of the classifier pool and having fixed relationship with respect to the surrounding tank structure, and top cover means rigidly intreconnecting said inner and said outer wall structure, whereby both said wall structures constitute between them said receiving chamber, and in which said discharge control means comprise a clear water column communicating with said receiving chamber to provide hydraulic balance relative to the pulp column in said pool, and means for maintaining said balance in a manner t attain said desired cut; and in which said water supply means comprise a supply chamber defined by said constriction plate, and by a solid .bottomstruc'ture underneath said lconstriction plate, said v( :ha'rnb'e'r having va water supply conduit leading through said outer wall structure. y

5. Apparatus according 'to claim `1, inwhichsaid horizontal bottom `of the ltank structure is in the nature of a false `bottom constriction plate,r"the waterfsupply means comprise a supply chamber 'defined said constriction plate and by a solid bottom marginally connected therewith, and said under'ow discharge means comprise controllable spigot valve means leading from the bottom strata of said pool.

6. Apparatus according to claim v1 in which 'said horizontal bottom of the tank structure `is "in the form of "a solid plate, said underflow discharge 'means comprise a controllable spigot valve means `leading directly from the bottom strata of said pool, 'and 'said water 'supply means comprise conduit means Aextending downwardly into said pool and having'jet emitting portions 'adjacent to and spaced from saidb'o'ttom for emitting .jets of water downwardly at an angle relative to said 'soli'd bottom. s s

7. Apparatus according to clair'n 1, in which said tank structure comprises an outer wall 'structure having a solid bottom, an inner wall structure surrounded by said outer wall structure and presenting free horizontal bottom edges, a horizontal false bottom member in the 'nature of a constriction plate spaced downwardly from said 'free horizontal bottom edges to provide outward passage for the coarse fraction particles, an u'p'stan'din'gA discharge weir Yprovided edgewise upon and along said bottom member 'and vspaced voutwardly from said passage in order that `coarse (fraction particles' in said pooi migrating to said passage may spill across said Weir into a receiving chamber defined below, said inner wall "structure 'together with said bottom member defni'ng'tfhe space Aof the classifier pool and having fixed relationship 2with respect to the surrounding tank structure, and ltop :cover means rigidly interconnecting said inner 'and Isaid 'outer wal-l structure, whereby both said wa-ll structures constitute between them said receiving chamber; in which said discharge control means comprise a clear column communicating with said receiving chamber to provide hydraulic balance relative to the pulp column in said pool, and means for maintaining said balance in a manner to attain said desired cut; in which said water supply means comprise a supply chamber defined by said constriction plate and by a solid bottom member underneath said constriction plate, said chamber having a water supply conduit leading through said outer wall structure; and in which said pulsation means comprise said constriction plate, means for movably mounting said constriction plate in substantially sealing relationship to said solid bottom to perform up and down vibratory movement, and drive means for imparting such vibratory movement.

8. Apparatus for the hydraulic classification treatment of pulp containing a mixture of particle sizes ranging from fine to coarse to effect sizeseparation of the mixture into a fraction of fines and a fraction of coarse particle sizes defined as undersize and oversize particles respectively, which apparatus comprises a tank structure for holding a classifying pool defined by a horizontal bottom and walls having overflow means for discharging the fines fraction from the top of the pool, controllable water supply means providing a flow of operating water for said pool emitting such operating water at a substantially uniform rate distributively in a manner whereby the water in effect rises in substantially uniform distribution from the bottom of the pool, and whereby in turn there are formed and maintained in said pool horizontal classification zones comprising substantially a sands zone of oversize particles adapted to be discharged through an outlet at the bottom, a fines zone of undersize particles adapted to discharge from the top, and an intermediate teeter zone containing a mixture of oversize and undersize particles, controllable discharge means for the oversize particles and actuating means responsive to the density of said teeter zone for automatically controlling said discharge means in response to density changes in said bed and to be automatically maintaining a desired fraction between the oversize and undersize discharging from said pool, characterized by the addition of a ow control device providing rhythmic interrupted flow of water superimposed upon the ow of said operating water and of mechanical pulsation means for superimposing straight pulsation upon said rhythmic interrupted ow, said pulsation means having an effective reciprocatory member for automatically increasing and decreasing a confined body of water communicating with said flow of operating water.

9. A method for the hydraulic classiiication treatment of a pulp containing a mixture of particle sizes to eiect a size separation of .the mixture into a tine fraction and a coarse fraction, comprising the steps of supplying said pulp to a coniined zone while removing a fine solids fraction from the top thereof and controllably removing a coarse solids fractionfrom the bottom thereof, supplying a first ow of liquid to said zone at a uniform rate and distributed in a manner whereby said liquid rises through said zone in substantially uniform distribution, and owing additional liquid in rhythmic interrupted flow and substantially uniform distribution upwardly through said zone. v

10. Method according to claim 9 wherein pulsations developed by said additional liquid are superimposed on said tirst flow of liquid by introducing said additional liquid into said iirst iiow of liquid prior to introduction v into said zone.

ranging from fine to coarse to effect the separation of said mixture into a i'ine fraction and a coarse fraction comprising a tank structure adapted to hold a classifying pool, means for discharging the fines fraction from the top of said pool, controllable water supply means providing a first ow of operating water for said pool at a substantially uniform rate and uniformly distributed from the bottom of said pool whereby there are formed and maintained in said pool horizontal classification zones comprising a lower zone of oversize particles to be discharged from a bottom outlet of said pool, a iines zone of undersize particles to be discharged from the top, an intermediate zone containing a mixture of coarse and tine particles in teeter condition, controllable discharge means for the oversize particles, anda second liquid supply means enabling a rhythmic interrupted iiowof liquid rising in substantially uniform distribution through said pool whereby said coarse oversize particles are induced to migrate to said bottom outlet.

14. The apparatus according to claim 13 wherein said second supply means superimposes said rhythmic interrupted iiow of Water upon said rst flow.

15. The apparatus according to claim 13 with the addition of mechanical pulsating means imposing additional distinct pulsations to said pool.

16. The apparatus according to claim 14 with the addition of mechanical pulsating means imposing additional distinct puisations to said pool.

References Cited in the tile of this patent UNITED STATES PATENTS 2,134,154 Smith Oct. 25, 1938 2,416,450 Macaulay Feb. 25, 1947 2,466,120 Nawman Apr. 9, 1949 2,677,463 Bolber May 4, 1954 2,708,517 Evans May 17, 1955 2,714,955 Marsten Aug. 9, 1955 2,714,956 Marsten Aug. 9, 1955 2,714,958 Evans Aug. 9, 1955 2,715,462 Coulter a Aug. 16, 1955 2,715,463 Fitch Aug. 16, 1955 

